A farm tyre normally comprises a toroidal carcass comprising a number of superimposed body plies and turned up at the ends about two annular beads. The carcass supports an annular tread; and between the carcass and the tread is interposed a tread belt, which comprises two superimposed tread plies comprising respective metal (typically steel) cords. Two tread ply wedges are interposed between the lateral ends of the two tread plies, to act as a cushion separating the tread plies. More specifically, at the join between the two tread plies, the opposite orientation of the cords of the two tread plies creates a critical point at which, when the tyre is stressed, deformation of the tread may result in slippage between the two tread plies. By absorbing and compensating for this slippage between the two tread plies, the tread ply wedges prevent it from resulting in local detachment (i.e. separation, failure) of the tread plies.
Patent Application DE102005049184A1, which constitutes the most recent state of the art, describes a tyre comprising: a carcass; a tread supported by the carcass; a tread belt interposed between the carcass and the tread and comprising an outer tread ply superimposed on an inner tread ply; and two tread ply wedges, each interposed between and locally diverging the lateral ends of the two tread plies. In this tyre, the two ends of each tread ply are covered with respective protective caps, each made of rubber and folded into a ‘U’ about the respective end.